jet mass for the option 7

[Sergei Chekanov]

Hi,

I'm trying to reconstruct the jet subjetiness using the option 7. I guess, this is the KT jet algorithm (not antiKT?). The problem I see is the when I retrieve jet momentum and look at the jet mass, I have very small values, close to 0. When I use the standard jets (the option 5, antiKT), the jet mass is correct. Is this a feature or a bug? I use Delphes 3.12

[Michele Selvaggi]

Hi,

option 7 corresponds to anti-kT with the so called "winner-take-all" procedure.
You can read more about it in here:

​http://arxiv.org/pdf/1401.2158v1.pdf

I am not sure whether what you observe is a feature. In principle the jet masses should be comparable.
I will run some tests tomorrow and let you know.

Michele

[Michele Selvaggi]

Dear Sergei,

concerning vanishing masses with winner-take)-all it was indeed an issue with fastjet
non properly calculating the jet four vector direction when other than E-scheme is being used.

For now, you can take "FastJetFinder.cc" from here (and recompile):
​https://github.com/delphes/delphes/blob/TestFastJet310b1/modules/FastJetFinder.cc

or wait for new release (that should come in days …).

Anyway, thank you for finding the bug.

Cheers,
Michele

[Pavel Demin]

This problem is fixed in d244bc9e8401e7ddf998acf45b845c99dfc0333c/git.

Closing this ticket.